This is not a BUG:hold shift and press crop,not respect the origin in some images,it means that some frames jump 1 pixel when playing animation.I think this is maybe because some images become odd pixels in width/height and some became even after croping.For example images with 93 pixel height and 94 pixel height have different origin y.
1.using always odd or even in crop (startx,starty),width,height.
2.calculate the mini area contain every frames before crop,and make every croped frame same size.
Some feature request:
1.keyboard shortcut and button for,navigate to previous and next frame.
2.number editor for hotspot x,y.
3.Feature to select multiple frames and delete.